Eric, I don't have a real good answer. Every 1977 thru 1987 Mainship 34 had the same mid bearing setup as OEM.
I am not sure if the oiriginal bearing was installed properly, but when I put in the new Aquamet shaft ahead of*my repower I installed my second new bearing (only because I had everything apart and I worked for Torrington Co and the bearings were free
) I made the proper drill spots for the set screws. My bearing actually had 2 setscrews and they both got spotted.
If the thrust load was transferred to the bearing then it must have been up to the task although I know it was not designed for thrust loading.